| Datacentre standards: an overview |
| Thursday, 30 November 2006 17:21 | |
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ADC Krone describes to Data Centre Management the key elements of the TIA-942 standard, a valuable tool in designing your datacentre and maximizing your investment For the past 20 years, cabling standards have been the cornerstone of ensuring proper design, installation, and performance of the network The Telecommunications Industry Association (TIA) revolutionised our industry when they released the first TIA-568 Commercial Building Telecommunications Wiring Standard, which describes the design, installation, and performance requirements for telecommunications cabling systems in commercial buildings. On the whole, standards have enabled our industry to effectively advance faster and further. Unfortunately, datacentres were historically designed in the absence of established standards. This had many network administrators faced with the challenge of choosing technologies and deciphering how to properly implement them into an often-undersized space that is responsible for securely and reliably providing all the existing and future services to an enterprise. In April 2005, the TIA responded with the TIA-942 Telecommunications Infrastructure Standards for Data Centres, the first standard to specifically address data centre infrastructure. Intended for use by data centre designers early in the building development process, TIA-942 covers the following: Site space and layout Proper space allocation for a data centre starts with ensuring that space can be easily reallocated to changing environments and growth. Designers must strike a balance between acceptable initial deployment costs and anticipated space required in the future. The data centre should be designed with plenty of flexible “white space”, empty space that can accommodate future racks or cabinets. The space surrounding the data centre must also be considered for future growth and planned for easy annexation. A large part of TIA-942 deals with facility specifications The standard recommends specific functional areas, which helps to define equipment placement based on the standard hierarchical star topology design for regular commercial spaces. Designing a data centre with these functional areas anticipates growth and helps create an environment where applications and servers can be added and upgraded with minimal downtime and disruption According to TIA-942, a data centre should include the following key functional areas: One or More Entrance Rooms This is the location for access provider equipment and demarcation on points, as well as the interface with campus cabling systems. The Entrance Room may be located either inside or outside the computer room, the portion of the data centre that houses data processing equipment. The standard recommends locating the entrance room outside of the computer room for better security. When located within the computer room, the Entrance Room should be consolidated with the MDA. It is possible that provider's cabling distances may require multiple Entrance Rooms for larger datacentres. Main Distribution Area (MDA) Similar to an MDF, the MDA is a centrally located area that houses the main cross-connect as well as core routers and switches for LAN and SAN infrastructures. The MDA may include a horizontal cross-connect (HC) for a nearby equipment distribution area. The standard requires at least one MDA and specifies installing separate racks for fibre, UTF, and coaxial cable in this location. One or More Horizontal Distribution Areas (HDA) Similar to a TR, the HDA serves as the distribution point for horizontal cabling and houses cross-connects and active equipment for distributing cable to the equipment distribution area. Like the MDA, the standard specifies installing separate racks for fibre, UTP, and coaxial cable in this location. It also recommends locating switches and patch panels to minimize patch cord lengths and facilitate cable management. The HDA is limited to 2000 connections, and the number of HDAs is dependent on the amount of cabling and overall size of the data centre. Equipment Distribution Area (EDA) Horizontal cables are typically terminated with patch panels in the EDA, the location of equipment cabinets and racks. The standard specifies installing racks and cabinets in an alternating pattern to create “hot” Zone Distribution Area (ZDA) The ZDA is an optional interconnection point in the horizontal cabling between the HDA and EDA. The ZDA can act as a consolidation point for reconfiguration flexibility or for housing freestanding equipment like mainframes and servers that cannot accept patch panels. Only one ZDA is allowed within a horizontal cabling run with a maximum of 288 connections. The ZDA cannot contain any cross-connects or active equipment. Backbone and Horizontal Cabling Within the data centre, backbone cabling provides connections between MDA, HDAs, and Entrance Rooms while horizontal cabling provides connections between HDAs, ZDA, and EDA. Optional backbone cabling can be installed between HDAs for redundancy. Each functional area must be located in such a way to prevent exceeding maximum cable lengths for both backbone and horizontal cabling. TIA-942 recommends the use of laser-optimized 50pm multimode fibre for backbone cabling because of its capability of supporting higher network speeds over longer distances while being more cost-effective to implement than singlemode fibre. For horizontal cabling, the TIA-942 standard recommends installing the highest capacity media available to reduce the need for re-cabling in the future. While Category 6 is the highest horizontal cabling media recognized by the standards today, verified 10 Gigabit Ethernet over UTP solutions are available and standards are in development. ADC believes serious consideration should be given to specifying an Augmented Category 6 solution for UTP-based data centre infrastructures. The TIA-942 standard also specifies maximum backbone and horizontal cabling distances based on the cabling media and applications to be supported in the data centre. Backbone fibre optic cabling is typically limited to 300m while horizontal copper cabling is limited to 100m. However, for small datacentres where the HDA is combined with the MDA, horizontal fibre cabling may extend to 300 meters. The TIA-942 standard provides several requirements and recommendations for cabling management The data centre must be designed with separate racks and pathways for each media type, and power and communications cables must be placed in separate pathways or separated by a physical barrier. Adequate space must be provided within and between racks and cabinets and in pathways for better cable management, bend radius protection, and access. For example, the standard requires a minimum of 3 feet in rows (4 feet recommended) and recommends aligning racks and cabinets on raised floors in a way that enables easy lifting of tiles Locating switches and patch panels to reduce the need for patching between cabinets and racks is also recommended. TIA-942 extends the TIA-606-A Administration Standard to data centres, which specifies a labelling scheme for all racks, cabinets, patch panels, patch cords, and cables. Tiered reliability To provide a means for determining specific data centre needs, the TIA-942 standard includes an informative ,annex with data centre availability tiers. These tiers are based on information from the Up-time Institute, a consortium dedicated to providing its members with best practices and benchmark comparisons for improving the design and management of datacentres. For each of the four tiers, the annex describes detailed architectural, security, electrical, mechanical, and telecommunications recommendations, and the higher the tier, the higher the availability. Tier descriptions include information like raised floor heights, watts per square foot, and points of failure. “Need,” or “N”, indicates the level of redundant components for each tier with N representing only the necessary system need. Construction cost per square foot is also provided and varies greatly from tier to tier, with Tier 3 costs double that of Tier 1. Breaking data centre reliability into these tiers provides designers with a method for qualifying certain aspects of the datacentre and objectively comparing one datacentre to another. • Susceptible to disruptions from both planned and unplanned activity • Less susceptible to disruption from both planned and unplanned activity • Enables planned activity without disrupting computer hardware operation, • Planned activity does not disrupt critical load and data centre can sustain at least one worst-case unplanned event with no critical load impact Environmental considerations Several environmental considerations exist within the TIA-942 data centre standard that are similar to the equipment room requirements set forth in previous TIA standards. These considerations include, but are not limited to, fire suppression, humidity levels, operating temperatures, architectural, electrical (power) and mechanical system specifications. Some of the requirements are dependent on the desired reliability tier described above. Power Determining power requirements is based on the desired reliability tier and may include two or more power feeds from the utility, UPS, multiple circuits to systems and equipment, and on-site generators. Determining power requirements requires careful upfront planning
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